color graphics in MCL

[gi01@gte.com (Glenn Iba)]

In using the built in colors (e.g. *red-color*, *orange-color*)
I find that some pairs of colors are indistinguishable on
my monitor (specifically red = orange, and blue = purple).
This happens both at home (Quadra 660av, NEC 3V monitor) and
at work (Mac IIfx, NEC MultiSync 6FGp).

Here's the kind of code I'm running, in case it yields a clue
to the problem:

(setf mywin (make-instance 'window :window-title "mywin"))

(with-focused-view mywin
    (with-fore-color *orange-color*
      (paint-rect mywin 0 0 120 120)))

The result looks identical if I use *red-color* instead of *orange-color*.
I also tried creating colors with MAKE-COLOR, but that didn't help
either.  My monitor is set to 256 colors, but I don't think that's the
problem -- when I use USER-PICK-COLOR I see a respectable orange, but
the number it returns shows up as red if used in the sample code above.
Is there something I have to do to make more colors available, or
there some inherent limitation??

Thanks in advance for any help!!

Glenn